Analog computer for decompression schedules

ABSTRACT

A device for computing a diver&#39;&#39;s decompression schedule which comprises a variable voltage D.C. power supply connected to the leading set of a plurality of resistor capacitor sets serially connected in electrical cascading relationship. Metering means are connected to at least a majority of the sets for indicating the highest voltage of the capacitors of the sets, both the metering means and power supply being calibrated in units of water depth for cascade charging the capacitors sequentially with time at a voltage corresponding to the time and depth of the dive and for cascade discharging of the capacitors sequentially with time to thereby produce a readout on the metering means to provide an ascent schedule for the diver.

United States Patent Todd 1451 Aug. 1, 1972 [54] ANALOG COMPUTER FORDECOMPRESSION SCHEDULES [72] Inventor: Gary P. Todd, 1716 Mark Lane,

Charleston, SC. 20852 22 Filed: Feb. 24, 1970 21 Appl.No.: 13,629

[52] 1.8. CI. .135/184, l28/002.l, 128/204, 235/l83, 320/00l [5| Int.Cl. ..G06g 7/60 [58] FieIdofSearch.......235/l83, I84, I97; l28/2.l,128/204; 320/ l Primary ExaminerFelix D. Gruber Attorney-T. RussellFoster [57] ABSTRACT A device for computing a divers decompressionschedule which comprises a variable voltage DC. power supply connectedto the leading set of a plurality of resistor capacitor sets seriallyconnected in electrical cascading relationship. Metering means areconnected to at least a majority of the sets for indicating the highestvoltage of the capacitors of the sets, both the metering means and powersupply being calibrated in units of water depth for cascade charging thecapacitors sequentially with time at a voltage corresponding to the timeand depth of the dive and for cascade discharging of the capacitorssequentially with time to thereby produce a readout on the meteringmeans to provide an ascent schedule for the diver.

9 Claim, 2 Drawing Figures PMENTEDAUB 1 m2 IN VEN TOR Gary 2 75d! 412ATTMIYIV ANALOG COMPUTER FOR DECOMPRESSION SCHEDULES This inventionrelates to underwater diving and more particularly to a computer for adecontpression schedule for a diver.

In diving operations in water by a person breathingpressurizedaintheinertgascomponentofthe airoforN,goesintosolutioninthebodyinanamountdeterminedbyboththedepthofthedivesndthetimespentby the diver under pressure corresponding to the depth. The amount ofinert gas or N, absorbed by the body continues until the condition knownas saturation occurs. During the ascent of a diver, as the pressure onthe diver is reduced, the excess of inert gas in the diver's body isexpelled until the concentration of inert gas in the body returns toequilibrium at atmospheric pressure. However, if the pressure on thediver's body is reduced too quickly as the diver ascends, the escape ofthe inert gas from the body occurs in an abnormal manner even to theextent of forming bubbles in the body as bubbles form in a carbonatedbeverage when the cap is removed. Such abnormal expulsion of the of theinert gas causes what is lrnown as decompression sickness usuallyreferred to as the bends" which not only can cause injury but if toosevere, death.

In order to avoid this decompression sickness, a diver remaining at acertain depth is required to follow a decompression time schedule inwhich his ascent is made by rising to various depths and remaining atthose depths for specified periods of time. Most diving schedules ortables have been formulated using the classical Haldane model andmodifying it from empirical data. Such present day decompressionschedules or tables have inherent limitations and deficiencies and mustbe used with caution. In the use of such present day tables, it isnecessary to include certain safety factors resulting in greater amountsof time being spent under compression than should be necessary. As canbe understood, the inclusion of such a safety factors results in theloss of useful time for the diver as well as failing to cop compensatepositively for the risk in operational diving.

Accordingly, a primary purpose of this invention is to provide a new andnovel computing device for programming a diver's decompression schedule.

Another object of this invention is to provide a new and novel analogcomputer for calculating a decompression schedule for a diver for anydiving time and depth within a wide range.

A further object of this invention is to provide a new and novel analogcomputer for programming a divers decompression schedule whicheliminates virtually all unnecessary diver's time during ascent ordecompression and which, at the same time, produces a maximum degree ofsafety for the diver during decompression.

A still further object of the invention is to provide a new and novelanalog computer for programming a divers decompression schedule which issimple and inexpensive in construction, which may be operated by arelatively unskilled individual and which permits the rapid calculationof a decompression schedule.

A still further object of this invention is to provide a new and novelanalog computer for programming a divers decompression schedule which isrugged in construction, which is composed of a minimum of parts andwhich may be utilized for either air dives wherein pressurizedatmospheric air is used or a mixture of O, and other non-reactive orinert gases such as helium and the like.

Other objects and advantages of the invention will become apparent forfrom the following description taken in connection with the yingdrawing. V

In general the object of this invention and other related objects areaccomplished by providing a plurality of resistor-capacitor setsserially connected in an electrical cascading relationship together witha variable voltage D.C. power supply connected by means including aswitch across the leading set of the plurality of sets for cascadecharging sequentially of the capacitors in the plurality of setsproportionately with time. The D.C. power supply is arranged to providea voltage corresponding to a selected water depth and metering meanscalibrated in units of water depth are connected to the capacitors in atleast the majority of sets for monitoring the voltage of all of thecapacitors to indicate in units of water depth the highest voltage ofthe monitored capacitors. A discharge resistor is also connected acrossthe leading resistor-capacitor set between the leading set and the powersupply for cascade discharging of the capacitors in the setssequentially and proportionately with time.

The novel features which are believed to be characteristic of theinvention are set forth with particularity in the appended claims. Theinvention, itself, however, both as to its organization and method ofoperation may be best understood by reference to the followingdescription taken in conjunction with the accompanying with theaccompanying drawing in which:

FIG. 1 is a schematic wiring diagram of the analog computer of theinvention; and

FIG. 2 is a front view of a meter incorporated in the analog computer ofFIG. 1

Referring now to the drawing, the analog computer of the invention,designated generally in FIG. 1 by the letter C, includes a plurality ofresistor-capacitor sets or ranks "-22, which in the illustratedembodiment are [2 in number. Each of the resistor capacitor sets 11-22include a capacitor Ila-22a and a resistor lib-22b respectively. Oneside of the capacitors 11a 420 are connected by means of conductors23-34 respectively to a common conductor 36 grounded as shown at 37. Theother side of the capacitors Ila-22a are connected by conductors 38-49to one side of each associated resistor llb-22b respectively and to oneside of the resistor of the next successive set so as to seriallyconnect the resistor-capacitor sets "-22 in electrical cascadingrelationship. v

The analog computer C also includes a variable voltage D.C. power supplySI arranged to be connected to a suitable source of power by means ofconductors 52. If desired, however, an integral source of power may beprovided such as a battery or the like. The D.C. power supply 51 isarranged to provide a voltage corresponding to a selected water depth aswill be explained hereinafter. To this end the D.C. power supply may beprovided with a manual regulating knob 53 by means of which the desiredoutput voltage on the power supply 5 l is selected.

Means including a switch 54 are provided for connecting the D.C. powersupply 51 across the leading set 11 of the plurality ofresistor-capacitor sets 11-22 for cascade charging sequentially of thecapacitors of the plurality of sets proportionally with time. Morespecifically, conductors 56, 57 are connected at n one end as shown inFIG. 1 to the power supply 51, conductor 56 being connected to thegrounded or common conductor 36 connected to one side of the sets 1 1-22and conductor 57 being connected to a conductor 58 connected to theother side of the sets 11-22 preferably through a variable resistor orpotentiometer 61 for a purpose to be explained hereinafter.

The potentiometer 61 includes a resistance 61a connected at one end tothe power supply conductor 57 and at its other end to the groundconductor 36. The potentiometer 61 also includes a movable contact 61bso that the power supply conductor 57 is connected through a selectedamount of resistance to conductor 58 thereby pennitting the voltageapplied to the leading resistor-capacitor set 11 to be reduced to avalue cor-- responding to the partial pressure of the inert gascomponent of air supplied to a diver. By way of example, in an air dive"the output voltage of the power supply 51 or the input voltage to thesets 11-22 is reduced percent as nitrogen or N comprises approximately80 percent of atmospheric air.

Associated with the power supply 51 is a discharge resistor 67preferably of the variable type which is connected at opposite ends toconductor 58, and the junction of conductors 36, 56. Thus the dischargeresistor 67 is arranged to be connected across the leadingresistor-capacitor set 11 by the connecting means including theconductors 36, 58 and switch 54. The discharge resistor 67 permitscascade discharging of the capacitors 11-22 sequentially andproportionally with time.

A charging capacitor 68 is also provided in association with the powersupply 51 which is connected across conductors 36, 58 in electricalparallel relationship with the discharge resistor 67. The capacitor 68is charged in accordance with the voltage output of the DC. power supply51 and applies this output voltage as reduced by the potentiometer 61 tothe leading set 11 for cascade charging of the capacitors 1 1a-22a ofthe plurality of sets 11-22.

The analog computer C includes metering means, preferably calibrated inunits of water depth, for monitoring the voltages of at least themajority of the capacitors Ila-22a of the plurality of sets 1 1-22 toindicate in units of water depth the highest voltage of the monitoredcapacitors. In the preferred embodiment, at least one set 11 andpreferably two sets 11, 12 are provided between the DC. power supply 51and the majority of sets connected to the metering means so that themetering means are connected to sets 13-22 as shown in FIG. 1.

More specifically, the metering means include a high impedance voltmeter70 grounded at one side at 71 as shown. A plurality of conductors 72-81are also provided each connected to one of the capacitors 130-220through conductors 40-49 respectively. The metering means also includesa connector switch 82 preferably of the single pole, double throw typehaving a movable contactor 82a and connected to the other side of thevoltmeter 70. One pole of the connector switch 82 is connected by meansof conductor 84 to a common conductor 86 connected to all of theconductor 72-81 so that in the solid line position of the connectorswitch contactor 82a all of the capacitors 13a-22a are monitored toindicate on the voltmeter the highest voltage present on the monitoredcapacitors Ilia-22a. in the preferred embodiment, the conductors 72-81each contain a diode 91 preferably of the type which has a very lowforward resistance and a very high reverse resistance for properfunctioning of the voltmeter 70 in monitoring the sets 13-22 in thesolid line position of the movable contactor 82a.

In order to alternately provide selective monitoring of the capacitors13a -22a in the sets 13-22 respectively the analog computer C includes aselector switch 92 having a plurality of terminals 93. The conductors72-81 are each connected to one of the selector switch terminals 93 onthe side of the diode 91 opposite the common conductor 86 by conductors94-103 respectively and means are provided for connecting all of theradial extension 104a for contacting engagement with each of theterminals 93 upon indexing movement of the contactor 104 by suitablemeans such as a manual operating knob 106. A stationary contact strip107 is also provide which is maintained in engagement with the rotatablecontactor 104 in any rotary position and the strip 107 is connected bymeans of conductor 108 through a diode 109 to the other pole of theconnector switch 82. In the dotted line position of the connector switchcontactor 820 the voltmeter 70 is connected to the selector switch 92and the selector switch 92 may be indexed to the desired position toobtain a readout on the voltmeter 70 for the voltage of each of thecapacitors individually in the sets 13-22.

As will be explained hereinafter, the voltmeter 70 is preferablycalibrated in units of water depth to permit a direct readout of theascent schedule for a diver. As shown best in FIG. 2, the dial face 111of the voltmeter 70 is provided with an arcuate strip 112 divided intouniform sections in each of which is indicated the depth, in incrementsof 10 feet, to which a diver may safely ascend as the dial indicator 113moves in the direction of the arrow 1 during the cascade discharging ofthe monitored capacitors 13a-22a in the sets 13-22 respectively. Thenumerals adjacent each dividing line for the sections in the strip 112represent the highest voltage monitored by the voltmeter 70.

The analog computer C also includes a normally open switch 1 16 which ispreferably manually operated and which includes a plurality of gangoperated contactors 1 17 each associated with one of the sets 1 1-22.All of the movable contactors 117 are connected to a conductor 118arrange to be connected to the conductor 58 through switch 54. Movementof the switch 116 to the right in the direction of the arrow S from thenormally open position of FIG. 1 moves all of the contactors 117simultaneously into contacting engagement with a terminal 1 19 on eachof the conductors 38-49 in the sets 11-22 to connect the capacitors 11a-22a respectively to the power supply 51 in the closed position ofswitch 54.

ln the operation of the analog computer of the invention, the variouscomponents of the computer C are selected to provide a selectedsaturation time for all of the capacitors 110-220 in the sets 1 1-22respectively in relationship to the time for a diver to becomecompletely saturated, that is, the time for a divers body to absorb themaximum amount of nitrogen in the body system reliably estimated to beapproximately 40 hours. By way of example, if the computer C saturatesin 200 minutes this would provide a 12:1 ratio so that the passage of 5seconds when the computer C is in use would be equivalent to 1 minute ofsaturation time for the diver.

in addition, the computer C is calibrated so that the voltages may beexpressed in units of water depth or feet of water and, in theillustrated embodiment, 1 volt is equivalent to feet of water. Thevoltage divider or potentiometer 61 is then set, as previouslydescribed, to provide a reduction of percent in the voltage output ofpower supply 51 this being the percentage of nitrogen in atmosphericair. The capacitors 11a -22a of the resistor-capacitor sets 11-22respectively are then initially charged uniformly at 3.3 volts or 33feet of sea water which is the equivalent of atmospheric pressure bysetting a voltage of 3.3 volts on the power supply 51 and moving theswitch 116 to the closed position, as previously described, with theswitch 54 in the closed position. The switches 54, 119 are then bothopened so that this initial charge of 3.3 volts remain on all of thecapacitors Ila-22a.

The power supply 51 is then set for an output voltage corresponding tothe depth of dive which, by way of example may be 9.3 volts for a 60foot dive this being the sum of 3.3 volts for atmospheric pressure and lfor each 10 feet of dive or 6 volts. Switch 54 is then closed andmaintained in the closed position for the time of dive, the time of divebeing controlled by the use of a suitable timer. However, as in theillustrated embodiment, a 12:1 ratio between real time and computer timeis employed, each 5 seconds which the switch 54 remains closed would beequivalent to 1 minute for the time of dive. Therefore, if a 30 minutedive is to be performed, the switch 54 would be maintained in the closedposition for 2 /2 minutes. During the time the output voltage of thepower supply 51 is supplied to the sets 11-22, capacitor 11a of set 11saturates rather quickly (approximately 5 seconds) and each of thesuccessive capacitors begin to saturate but at a successively lower ratefor the succeeding capacitors with the voltage spilling over into thenext successive capacitor according to the difference in voltage betweencapacitors.

After the time of dive is completed and ascent of the diver is to begin,connector switch 82 having been positioned in the solid line position ofFIG. 1, the depth indicated by the needle 113 on the strip 112 of thevoltmeter 70 is read and the voltage of the power supply 51 is reducedto the level indicated on the voltmeter 70 to begin the desaturation orcascade discharging of the capacitors Ila-22a into the dischargeresistor 67. As has been explained, the voltmeter 70 will read thehighest voltage in all of the monitored capacitors of 130-22 and thedepth figure indicated on the voltmeter 70 will be the first safe stopduring the divers ascent. Preferably, the reduction in voltage on thepower supply 51 is accomplished by reducing the volt age each 5 to theindicated depth on the voltmeter at the end of 5 second intervals sinceit is anticipated that 1 minute would be require by the diver to ascendbetween each 10 foot stop.

ln event the needle 1 13 moves in the direction of arrow 1 as thecapacitors discharge to the new lower section in 10 foot increments inless than 5 seconds, the reduction in voltage of the power supply 51should continue so that when decompression is actually required a depthwill be reached at which the meter will not drop to the next shallowerstop within the 5 second period and that depth will become the firstdecompression stop remaining so until the voltmeter goes to the nextstop depth.

At each stop depth, the voltage on the power supply 51 is kept at thedepth of that stop until the voltmeter 70 indicates it is safe to ascendto the next shallower stop. The duration of each stop is recorded andascent is continued at the beginning of the next full 5 seconds asexplained above.

The table below is representative of the manner in which the computer Cand the voltmeter 70 are calibrated. For instance, where the diver is atthe 60 foot depth during ascent, the departure pressure is 98 feet ofwater or 9.8 volts so that when the voltmeter needle 113 passes thedividing line between the 60 and 50 foot stop depths corresponding to avoltage of 9.8 volts, the diver is then permitted to ascend to the 50foot stop depth.

TABLE 1 ABS. Departure Depth Pressure N, Pressure Pressure (feet) (it.of H,O) (ft. of H,O) (ft. of H,0)

0 33 26 10 43 34 48 20 53 42 58 30 63 S0 68 40 73 58 I8 50 83 66 88 6093 74 98 70 103 82 108 l 13 l 18 90 123 97 12B I33 138 1 I0 143 l 13 148153 121 158 163 129 168 I73 137 178 150 I83 188 By compiling the firststop depth for a dive having a predetermined depth and duration togetherwith the various stop depths during ascent and the time at each stopdepth, a complete ascent schedule may be programmed very quickly sincethe ratio between real time and computer time is such that dives of anydepth or duration over a wide range with a maximum of safety and aminimum of loss time may be programmed in a relatively short space oftime. The computer C of the invention may be readily minaturized andoperated by a relatively unskilled operator since the calibration of thecomputer is such that although voltages are determinative of theresults, all of the settings and readings are in feet making itrelatively simple and easy to compile a divers ascent shedule. Theselector switch 92 is preferably included in the computer C so that whenthe connector switch 82 is moved to the dotted line position of FIG. 1,the switch 92 may be indexed throughout all of the terminals 93 as thetime for the dive to end approaches to indicate generally where thefirst stop depth of any duration may be expected. It has been found thatby providing sets ll, 12 which are not connected to the voltmeter 70 andselector switch 92, a more accurate reading is obtained in that thecapacitors 1 la, 12a of these two sets saturate rather quickly inapproximately seconds and will follow the divers ascent so rapidly as tobe of relatively little value except in fast ascents.

While there has been described what at present is considered to be thepreferred embodiment of the invention, it will be understood by thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention.

Having thus described the invention, what is claimed 1. An analogcomputer for programming a decompression schedule comprising, incombination, a plurality of resistor-capacitor sets interconnectedtogether with the resistors in said sets in serially connectedrelationship and with the capacitors in said sets in parallel connectedrelationship for cascade charging of said capacitors, a variable voltageDC power supply for providing a voltage equivalent to a selected waterdepth, means for connecting said DC. power supply across the leading setof said resistor-capacitor sets for cascade charging sequentially of thecapacitors in said sets proportionally with time to simulate the timespent by a diver at a predetermined diving depth, metering means formonitoring the voltages of at least the majority of capacitors of saidplurality of sets to continuously indicate the highest voltage of saidmonitored capacitors and means for cascade discharging sequentially ofthe capacitors in said plurality of sets proportionally with time toprovide a timed ascent schedule for a diver corresponding to the voltagereadout on said metering means.

2. An analog computer in accordance with claim 1 wherein said meteringmeans is calibrated in units of water depth to permit a direct readoutof the ascent schedule for said diver.

3. An analog computer in accordance with claim 1 wherein said connectingmeans includes a variable resistor for reducing the voltage applied tosaid leading resistor-capacitor to set by said DC. power supply to avoltage level corresponding to the partial pressure of the inert gascomponent of air supplied to said diver.

4. An analog computer in accordance with claim 1 including a normallyopen switch for connecting all of the capacitors in said plurality ofsets to said D. C. voltage supply for simultaneously charging all ofsaid capacitors to a voltage corresponding to atmospheric pressure.

5. An analog computer in accordance with claim 1 wherein said meteringmeans includes a voltmeter, a plurality of conductors each connected toone of said capacitors in said majority of resistor-capacitor sets and aconnector switch for connecting all of said of plurality of conductorsto said voltmeter for indicating the highest voltage on said monitoredcapacitors.

6. An analog computer in accordance with claim 5 including a selectorswitch having a plurality of terminals, means for connecting each ofsaid terminals to one of said capacitors in said majority ofresistorcapacitor sets, means for connecting all of said selector switchterminals to said connector switch, said connector swi h bei ovable betwn ti t ition for connec t fng sat vo meter to sm pliirality t conductorsand a second position for connecting said voltmeter to said selectorswitch to obtain a readout on said voltmeter of the voltage on each ofsaid capacitors individually by selective positioning of said selectorswitch.

7. An analog computer in accordance with claim 6 including a diode ineach of said plurality of conductors for connecting said capacitors tosaid voltmeter.

8. An analog computer in accordance with claim 7 wherein said pluralityof resistor-capacitor sets includes at least one set between said D. C.power supply and said majority of sets connected to said metering means.

9. An analog computer in accordance with claim 8 wherein two seriallyconnected resistor-capacitor sets are provided between said D. C. powersupply and said majority of sets connected to said metering means.

1. An analog computer for programming a decompression schedulecomprising, in combination, a plurality of resistor-capacitor setsinterconnected together with the resistors in said sets in seriallyconnected relationship and with the capacitors in said sets in parallelconnected relationship for cascade charging of said capacitors, avariable voltage D.C. power supply for providing a voltage equivalent toa selected water depth, means for connecting said D.C. power supplyacross the leading set of said resistor-capacitor sets for cascadecharging sequentially of the capacitors in said sets proportionally withtime to simulate the time spent by a diver at a predetermined divingdepth, metering means for monitoring the voltages of at least themajority of capacitors of said plurality of sets to continuouslyindicate the highest voltage of said monitored capacitors and means forcascade discharging sequentially of the capacitors in said plurality ofsets proportionally with time to provide a timed ascent schedule for adiver corresponding to the voltage readout on said metering means.
 2. Ananalog compUter in accordance with claim 1 wherein said metering meansis calibrated in units of water depth to permit a direct readout of theascent schedule for said diver.
 3. An analog computer in accordance withclaim 1 wherein said connecting means includes a variable resistor forreducing the voltage applied to said leading resistor-capacitor to setby said D.C. power supply to a voltage level corresponding to thepartial pressure of the inert gas component of air supplied to saiddiver.
 4. An analog computer in accordance with claim 1 including anormally open switch for connecting all of the capacitors in saidplurality of sets to said D. C. voltage supply for simultaneouslycharging all of said capacitors to a voltage corresponding toatmospheric pressure.
 5. An analog computer in accordance with claim 1wherein said metering means includes a voltmeter, a plurality ofconductors each connected to one of said capacitors in said majority ofresistor-capacitor sets and a connector switch for connecting all ofsaid of plurality of conductors to said voltmeter for indicating thehighest voltage on said monitored capacitors.
 6. An analog computer inaccordance with claim 5 including a selector switch having a pluralityof terminals, means for connecting each of said terminals to one of saidcapacitors in said majority of resistor-capacitor sets, means forconnecting all of said selector switch terminals to said connectorswitch, said connector switch being movable between a first position forconnecting said voltmeter to said plurality of conductors and a secondposition for connecting said voltmeter to said selector switch to obtaina readout on said voltmeter of the voltage on each of said capacitorsindividually by selective positioning of said selector switch.
 7. Ananalog computer in accordance with claim 6 including a diode in each ofsaid plurality of conductors for connecting said capacitors to saidvoltmeter.
 8. An analog computer in accordance with claim 7 wherein saidplurality of resistor-capacitor sets includes at least one set betweensaid D. C. power supply and said majority of sets connected to saidmetering means.
 9. An analog computer in accordance with claim 8 whereintwo serially connected resistor-capacitor sets are provided between saidD. C. power supply and said majority of sets connected to said meteringmeans.